Microstructure-independent acoustoelastic measurement of stress

Measurements are reported of the velocities of horizontally polarized shear waves (fundamental mode) propagating in the plane of aluminum plates under tensile loads applied parallel to the rolling direction. In agreement with the predictions of previous theories, the applied stress is found to be predicted by the expression 2C(ΔV/V), where C is the appropriate second-order shear elastic constant and ΔV/V is the fractional difference in velocities of waves propagating parallel and perpendicular to the load. The data show that, whereas the individual velocities are strongly influenced by microstructure, the stress prediction based on their difference is not. Included are results illustrating the effects of preferred grain orientation and plastic deformation.